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Earth has a new moon. Or, to be more precise, a quasi-moon.
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A tiny asteroid discovered this year, dubbed 2023 FW13, has been found to circle the sun in sync with the Earth, in an eccentric orbit that takes it halfway to neighbouring Mars and Venus while it executes a long, lazy orbit around our planet.
The little moon is only about 20 metres wide and never comes closer than about 14 million km from Earth, so it’s too small to be seen with the naked eye. It was discovered by the Pan-STARRS survey telescope on the Hawaiian island of Maui, and confirmed by the Minor Planet Center on April 1.
Earth’s main moon, in comparison, has a diameter of 3,500 km, and orbits the Earth at an average distance of about 380,000 km. 2023 FW13 is some 36 times farther away at the nearest point in its orbit.
Scientists calculated the path of the space rock and hypothesized that it’s been circling the Earth for at least 2,100 years and will keep it up for another 1,700 years or so until it wanders off into deep space again. “It seems to be the longest quasi-satellite of Earth known to date,” French astronomer Adrien Coffinet told Sky & Telescope magazine after running the numbers on the moonlet.
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Alan Harris of the Space Science Institute noted that, with an estimated 2 million near-Earth asteroids of 2023 FW13’s size or larger, the odds are that there are several quasi-moons circling the Earth at any one time.
In fact, in 2016 astronomers discovered another quasi-moon, 2016 HO3, which eventually took the name Kamo’oalewa, a Hawaiian word meaning “oscillating fragment.” It’s been a companion of Earth for at least a hundred years and is expected to hang around for several hundred more.
Scientists think Kamo’oalewa may be a piece of the moon that was knocked off by an asteroid collision. China plans to launch a probe to visit the roughly 50-metre wide moonlet in 2025 and collect a sample.
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June 02, 2023 at 05:05PM
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Earth picked up a new moon about 2,100 years ago. Astronomers just found it - National Post
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